boundingbox.h

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/*    Copyright 2014 MongoDB Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

#pragma once

#include <vector>

#include "mongo/db/jsobj.h"
#include "mongo/geo/constants.h"
#include "mongo/util/assert_util.h"

namespace mongo {
namespace geo {

template <typename TCoordinates>
class BoundingBox {
public:
    BoundingBox(const TCoordinates& min, const TCoordinates& max);

    explicit BoundingBox(const BSONObj& bson);

    TCoordinates getMin() const {
        return _min;
    }

    TCoordinates getMax() const {
        return _max;
    }

    BSONObj toBSON() const;

    BSONArray toBSONArray() const;

    BSONArray toNestedBSONArray() const;

private:
    TCoordinates _min;
    TCoordinates _max;
};

template <typename TCoordinates>
BoundingBox<TCoordinates>::BoundingBox(const TCoordinates& min, const TCoordinates& max)
    : _min(min), _max(max) {}

template <typename TCoordinates>
BoundingBox<TCoordinates>::BoundingBox(const BSONObj& bson) {
    BSONElement bbox = bson.getField(kBoundingBoxFieldName);

    // Ensure bson defines a bounding box.
    uassert(0, "bson argument to BoundingBox ctor must define the field \"bbox\"", !bbox.eoo());

    std::vector<BSONElement> bboxCoords = bbox.Array();

    // The GeoJSON spec dictates that bboxCoords is an array of
    // length 2*n, where n is the number of dimensions represented
    // in the contained geometries.
    const size_t n = TCoordinates::dimensionality();
    uassert(0,
            "bbox field must have exactly 2 * n elements, where n is the number of dimensions "
            "in the coordinate system",
            bboxCoords.size() == 2 * n);

    // Construct _min with the first n elements and _max with the second n elements.
    std::vector<double> minCoords, maxCoords;
    for (size_t i = 0; i < n; ++i) {
        minCoords.push_back(bboxCoords[i].Double());
        maxCoords.push_back(bboxCoords[n + i].Double());
    }
    _min = TCoordinates(minCoords);
    _max = TCoordinates(maxCoords);
}

template <typename TCoordinates>
BSONObj BoundingBox<TCoordinates>::toBSON() const {
    return BSON(kBoundingBoxFieldName << toBSONArray());
}

template <typename TCoordinates>
BSONArray BoundingBox<TCoordinates>::toBSONArray() const {
    BSONArrayBuilder bab;
    std::vector<double> minCoords = _min.getValues();
    std::vector<double> maxCoords = _max.getValues();
    for (size_t i = 0; i < minCoords.size(); ++i)
        bab.append(minCoords[i]);
    for (size_t i = 0; i < maxCoords.size(); ++i)
        bab.append(maxCoords[i]);
    return bab.arr();
}

template <typename TCoordinates>
BSONArray BoundingBox<TCoordinates>::toNestedBSONArray() const {
    BSONArrayBuilder minBab, maxBab;
    std::vector<double> minCoords = _min.getValues();
    std::vector<double> maxCoords = _max.getValues();
    for (size_t i = 0; i < minCoords.size(); ++i)
        minBab.append(minCoords[i]);
    for (size_t i = 0; i < maxCoords.size(); ++i)
        maxBab.append(maxCoords[i]);
    return BSON_ARRAY(minBab.arr() << maxBab.arr());
}

}  // namespace geo
}  // namespace mongo